1. Field of the Invention
This invention relates to devices for recording and reading magnetically stored data for a magnetic disk memory device and more particularly it is concerned with data recording and reading device of the type described which uses a step motor as a source of drive force.
2. Description of the Prior Art
A magnetic disk memory device is provided with data recording and reading device for positioning a magnetic head on a track on a magnetic disc for magnetically recording or reading a particular item of data. One type of data recording and reading device of the prior art using a step motor comprises a carriage for supporting a magnetic head, guide rods for guiding the carriage in its linear motion, a belt secured at one end thereof to the carriage, and the step motor for moving the carriage in linear motion by driving the belt. In this type of data recording and reading device disclosed in U.S. Pat. No. 3,946,439, the belt is trained over a motor pulley of the step motor and another pulley and the carriage is supported on the belt. In this device, the motor pulley rotating in synchronism with the motor is rotated stepwise to move the belt, to thereby move the carriage. Another type of data recording and reading device is disclosed in U.S. Pat. No. 4,161,004 which comprises a mechanism including a motor pulley on which a belt is trained and a carriage having the belt screwed at opposite ends thereof, wherein rotation of the motor pulley drives the carriage. The data recording and reading devices of the prior art are intended to move a carriage of large mass at high speed in linear motion.
Owing to the inertia of the carriage, difficulties would be encountered in effecting positioning of the magnetic head at high speed with a high degree of accuracy. Particularly in an application wherein the magnetic head is positioned on a desired track in a period of time on the order of milliseconds on a magnetic disc on which tracks are located concentrically with a spacing interval of no greater than about 0.13 mm, the accuracy with which the magnetic head is positioned on the desired track would be greatly reduced due to the inertia of the carriage.